Ink jets commonly employ a transducer associated with a chamber adjacent the orifice such that the volume of the chamber is contracted and expanded in response to the state of energization of the transducer.
In a continuous ink jet, a constant flow of ink under pressure by means of a suitable pump so as to produce a constant flow of ink to the chamber wherein the contraction and expansion of the chamber interrupts the continuous flow of ink so as to break up a stream of ink flowing from the orifice into individual droplets. The individual droplets are either projected toward the copy medium or deflected into a catcher. p In an impulse ink jet, droplets of ink are only projected from the orifice on demand, i.e., droplets are projected only when the transducer is energized or deenergized depending upon the configuration of the ink jet. Although no pump is utilized in an impulse ink jet to maintain a stream of ink under pressure as in the case of the continuous ink jet, a pump may still be required during priming so as to provide the chamber of the impulse ink jet with an adequate supply of ink. In addition, a pump may be utilized in an impulse ink jet for purging, i.e., clearing the jet of any dry ink or other debris which might interfere with the projection of droplets from the orifice. It may also be desirable to provide a catcher in an impulse ink jet and associated pumping means for producing subatmospheric pressure at the catcher in accordance with the invention of copending application Ser. No. 203,582 filed Nov. 3, 1980.
From the foregoing, it will be appreciated that different requirements may be imposed on pumps utilized in ink jet applications. For example, in the case of priming, it is desirable to have the capability to meter out a predetermined amount of ink. Metering may also be important in purging in addition to sufficiently high pressure to relieve a clogged nozzle condition. Of course, all of this must be done with reliability.
Another requirement as set forth in copending application Ser. No. 203,583 filed Nov. 3, 1980 is disposability of at least a portion of the ink jet system for ease of operator maintenance. If the pump itself is to be disposable with the rest of the system, it must of course be relatively inexpensive. Additionally, it is desirable that any portion of the pump which is not disposable be easily interfaced with the disposable system. It is further desirable to minimize the risk of contaminating the ink supply.